1. Field of the Invention
The invention relates generally to the field of pulse transmission communications. More particularly, the invention relates to pulse transmission, spread-spectrum modes of low-power radio communications.
2. Discussion of the Related Art
Prior art time-domain communications techniques are known to those skilled in the art. The bandwidth and center frequency of a conventional time-domain transmission are both explicit functions of the pulse width.
In these techniques, the controllable parameters are the pulse width and power. These techniques normally allow only 1 bit to be conveyed per transmitted pulse, thereby limiting their communications usefulness.
A problem with this existing technology has been that the parameters of pulse width and power effectively provide only two degrees of freedom. This constraint severely limits the flexibility of the prior-art time-domain techniques. Therefore, what is required is an approach to time-domain communications that provides more degrees of freedom.
Another problem with this existing technology has been that only one bit can be encoded per transmitted pulse. This constraint severely limits the data bandwidth of the prior art time-domain techniques. Therefore, what is also required is an approach to time-domain communications that permits more than one bit per pulse to be communicated.
Heretofore, the requirements of providing additional degrees of freedom and communicating multiple bits per pulse have not been fully met. What is needed is an approach that can address both of these requirements. The invention is directed to meeting these requirements, among others.
The main object of the invention is to provide a versatile, multi-bit, very broadband, high bit-rate data communications method. Another goal of the invention is to use higher-order derivatives of pulsed (time-domain) signals to satisfy the above-discussed requirements of providing additional degrees of freedom and communicating multiple bits per pulse which, in the case of the prior art, are not simultaneously satisfied.
One embodiment of the invention is based on a method of pulse-transmission communications, comprising: generating a modulated pulse-signal waveform; transforming said modulated pulse-signal waveform into at least one higher-order derivative waveform; and transmitting said at least one higher-order derivative waveform as an emitted pulse. Information is preferentially encoded as the derivative order and phase; alternatively, time derivatives between pulses can also encode information. In the latter case, the higher-order derivative pulse provides flexible control over bandwidth and band center-frequency, thus alleviating noise and other interference problems. Another embodiment of the invention is based on an electromagnetic waveform, comprising: an emitted pulse that is produced from at least one higher-order derivative waveform of a modulated pulse-signal waveform. Another embodiment of the invention is based on an apparatus based on an array of various higher-order derivative-pulse generators, each of which is modulated by an information signal. The modulated derivative pulses are summed, amplified, and coupled to a transmission medium (antenna, cable, optical fiber, etc.) The complementary receiver recovers the modulated pulses via standard correlation.